As more people are networked through their machines, transmitting, receiving and storing vital information, information technology departments face greater challenges keeping those networks operational and often from remote locations. In many instances, the network server needs to be rebooted in order to resolve issues or in the course of routine maintenance. When a computer (e.g., server) is booted up, an operating system is loaded into the computer's main memory. Once loaded users may run applications, or in case of a server, network services and applications are started to service its respective client machines. Additionally, for PC based systems, after booting up, the system may utilize a memory mapped I/O (MMIO) base address register located above one megabyte (1 MB) to access all available AHCI (advanced host controller interface) registers connected to a multitude of SATA (serial advanced technology attachment) devices.
In PC (personal computer) based systems, programs such as BIOS (basic input/output system), option ROMs (read-only memory), OSs (operating systems), or other programs are written to start up in ‘real mode’ (e.g., Intel's® 8086 mode). In real mode, a program cannot access memory above 1 MB. Because the MCH (memory controller hub—north-bridge) doesn't forward memory mapped I/O spaces above 1 MB down to ICH (I/O controller hub—south-bridge) and the memory space below 1 MB is also the main memory of the system, there is no memory to be allocated to AHCI accesses. Therefore, a real mode program is limited to using the IOBARs (0-4) (I/O base address registers) to access SATA devices; this limits the number of available devices it can access for boot up or any other purpose to 4.